SkyGlance — What's Flying Above You

SkyGlance

Ask Claude what's flying above you.

Live positions, real aircraft identities, routes, photographs — and a memory of everything that's passed over.

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Quick Start

claude mcp add skyglance -- uvx --from skyglance skyglance

Then ask Claude: *"What's flying over me right now?"*

Needs uv. Its installation guide covers every platform. No API keys — every data source here is free.

Set your location so you can stop repeating it, and so SkyGlance can build a sighting history:

claude mcp add skyglance \

-e SKYGLANCE_HOME_LAT=40.71 -e SKYGLANCE_HOME_LON=-74.01 \ -- uvx --from skyglance skyglance

Install as a Claude Code plugin

Ships the server together with the sky skill, which teaches Claude how to read elevation angles and how to talk about aircraft to someone who has never spotted one.

/plugin marketplace add darshjoshi/skyglance-mcp

/plugin install skyglance@skyglance

SkyGlance Spotter: the Claude directory edition

The repository root is also a plugin, SkyGlance Spotter (skyglance-spotter), built for Anthropic's Claude plugin directory. It runs the same server from this repository's source and differs in four ways:

• Two tools are left out. military_aircraft and privacy_blocked_aircraft aren't included, and search_aircraft has no military filter. Those features exist to follow aircraft whose operators or owners would rather not be followed.
• History is opt-in. Sighting history is recorded only after you switch on Record sighting history in the plugin's settings.
• Settings instead of environment variables. Home latitude and longitude are optional plugin settings.
• History lives in the plugin's data folder. The history database is kept in a folder Claude Code preserves across plugin updates and deletes when you uninstall. The Python environment uv builds on first start sits in the plugin folder and is rebuilt after each update.

/plugin marketplace add darshjoshi/skyglance-mcp

/plugin install skyglance-spotter@skyglance

It needs uv. On first start, uv run --locked installs the exact dependency versions in uv.lock (the MCP SDK, httpx and their dependencies) from PyPI, which takes a few seconds. SkyGlance Spotter works in Claude Code and Cowork. It runs locally, so it isn't available in claude.ai chat.

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What you can ask

"What's flying over me right now?"         → ranked by what you'd actually notice

"What's about to pass overhead?" → but only 90 seconds ahead, honestly "What is that plane?" → type, operator, route, photograph "Where is flight UAL123?" → anywhere in the world "Any A380s airborne?" → 44 of them, right now "Any military aircraft near me?" → and any emergencies, worldwide "Have I ever seen this plane before?" → your own history says "What's the closest one ever?" → your personal records "Can I even see anything tonight?" → cloud, visibility, daylight

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Why it's shaped this way

"Over you" is an angle, not a distance. A radius filter returns an airliner at 38,000 ft that is 19 km away — sitting 32° above the horizon, a speck near the treeline — and gives it the same weight as a helicopter at 800 ft, at 0.7°, invisible behind buildings. SkyGlance computes the elevation angle, the compass bearing to look, and the slant range, so an answer tells you *where to point your face*.

It won't predict further than it can. Straight-line extrapolation from track and ground speed is accurate to about 0.11 km at 30 seconds. At four minutes the median miss is 6 km and 77% of aircraft are more than 2 km off, because aircraft on approach turn constantly. So countdowns stop at 90 seconds and anything beyond is reported as "inbound" with no number attached.

It knows when it can't see. Free ADS-B coverage comes from volunteers with receivers on their roofs. Dense Europe, US and East Asia get 90–95% of what a commercial feed shows. Oceans, Africa and central Asia get near zero. When results are thin, SkyGlance says so rather than implying an empty sky.

Your coordinates are rounded before they leave. Feed queries are coarsened to two decimal places (~1.1 km) so no volunteer feed operator gets a rooftop-accurate log of where you are and when you're awake. Bearing and elevation are still computed locally from your exact position, so what you're told to look at stays precise. There's a test that fails if an uncoarsened coordinate ever reaches a feed.

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The 24 tools

How this compares to Flightradar24

SkyGlance is a question-answering tool, not a map, so the comparison is about *what you can find out* rather than what you can look at.

The honest summary: for spotting and identification — *what's above me, what is that, where has it been, how many 747s are up* — SkyGlance covers what FR24 charges Silver and Business for, at $0. For travel logistics — *is my flight delayed, what gate* — it cannot compete, because that's licensed schedule data rather than ADS-B. And FR24's satellite network sees oceanic traffic that volunteer receivers simply cannot hear.

So: a strong replacement for the enthusiast half, not for the passenger half.

What it deliberately can't do

Free ADS-B carries positions, not schedules. So there are no delays, no ETAs against a timetable, no gates or terminals, and no way to search "flights from JFK to London today" — route lookup only runs the other way, from a callsign you already have. track_history is a rolling ~24-hour window, not an archive.

These aren't on a roadmap. They're a different data product (Cirium, OAG, FlightAware), and buying one would end the no-API-keys story. The tools refuse these questions explicitly rather than estimating, and the bundled skill tells Claude to do the same.

Sighting history

With SKYGLANCE_HOME_LAT/LON set, SkyGlance polls your sky once a minute in the background and records every pass. That's what makes the questions no live feed can answer possible: *have I seen this tail before, is this type new here, what's the lowest anything has ever come over.*

• Stored locally in SQLite at ~/.skyglance/sky.db. Nothing is uploaded anywhere.
• Only one process polls, even with several Claude sessions open — a pid-stamped lock enforces it, so volunteer feeds don't get hit N times over.
• Turn it off with SKYGLANCE_POLL=0.
• Honest limit: passes are inferred from snapshots a minute apart, so a fast low pass between polls isn't recorded. poller_status tells you the interval.

Configuration

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Where the data comes from

Seven free services, no API keys, $0/month. Full terms in NOTICE.md.

Both position feeds are queried in parallel and merged, not failed over. Measured over Newark on 2026-08-02, when a third feed (airplanes.live) was still in the mix: 52 aircraft from the best single source, 61 from the union — 17% more. Merging buys coverage as well as redundancy. airplanes.live has since closed its API to anyone who hasn't contacted them first, so SkyGlance no longer queries it.

Each source sits behind a circuit breaker (three strikes, 30-second cooldown). These are volunteers paying for their own bandwidth, with no SLA and no obligation to anyone. If both fail, the last good snapshot is served flagged stale rather than an error — a 40-second-old aircraft beats a spinner.

Not suitable for anything operational. Dispatch, safety, ATC-adjacent — buy a commercial feed. The upstream terms say the same.

Network access

SkyGlance only makes outbound requests to fetch public aviation data. It sends each service only what the lookup needs: a location rounded to two decimal places (about 1.1 km), or an aircraft identifier, airline code or airport code. It never sends your conversation, files or any account details, and it uses no API keys.

Each service has its own terms. NOTICE.md lists them and explains how SkyGlance meets them.

Two development-only files in this repository also make network requests. Neither the server nor the plugin ever runs them:

• tools/build_airports.py downloads the public-domain OurAirports CSV from davidmegginson.github.io